After microvascular decompression of the trigeminal nerve for relief of tic douloreux, about 70% of patients with a positive history of cold sores develop herpes lesions with onsets 2-5 days after surgery. We will administer human interferon to about 20 patients per year in order to modify the disease or reduce its frequency, comparing the effects of early (pre surgery) and late (post surgery) treatment with a placebo control. Interferon in serum and throat washes will be assayed. The patients, and others including those undergoing VIIth nerve surgery for hemi-facial spasm will be followed clinically, virologically and immunologically. The purpose of this phase of the study is to examine events occurring between the time of stimulus (surgery) and the appearance of overt lesions. This early phase of the pathogenesis of recurrent herpes is not usually available to investigators.